1. Field of the Invention
The present invention relates to a method of data transmission in a communication system.
2. Description of the Related Art
A conventional network that performs packet communication includes communication devices called nodes that are interconnected by links. Information is transmitted in the network from a source node to a destination node through communication paths that include relay nodes. A relay node only sorts the packets based on the data in the packets and redirects them towards the corresponding destination nodes. In other words, a relay node does not perform any process on user data in a packet.
In addition to sorting the packets, data encoding can be performed at each relay node by using a network coding technology to efficiently transmit the data over the network. For a more complete description of the network coding technology, reference may be had to, e.g., nonpatent literature as follows:
R. Ahlswede et al., “Network information flow”, IEEE trans. on Information Theory, Vol. 46, No. 4, July 2000, pp. 1204-1216;
Yamamoto Miki, “Network coding”, Journal of Institute of Electronics, Information and Communication Engineers (IEICE), Vol. 90, No. 2, February 2007, pp. 111-116; and
S-Y. R. Li et al., “Linear network coding”, Vol. 49, No. 2, February 2003, pp. 371-381.
Main advantage of the network coding, apart from allowing efficient use of communication resources such as a bandwidth, is that it provides better data confidentiality. Concretely, in the network coding technology, encoding process is performed on the data in each packet at each relay node, so that even if an outsider succeeds in tapping the data during transmission, it is difficult to break the data code thereby maintaining the data security.
However, quantitative evaluation of the security level is not performed in the abovementioned network coding technology. Thus, it is difficult to determine the security level of data encoding thereby failing to ensure that the data security is maintained at all the time.